The most important and most frequently used interferometer is the Michelson one with its many modifications. The light of a mostly monochromatic light source is split up by a semitransparent, reflecting surface of an optical beamsplitter into two partial beams. After its reflection by two mirrors, the beamsplitter recombines both of them to a single light beam. This union leads to interference fringes whose contortion or displacement constitutes a measure for the difference of the optical paths between the two partial beams.
The known interferometers can be used for a great number of tasks, e.g. for:
measuring the spectral composition of the light; PA0 measuring the velocity of light; PA0 measuring the imperfections of optical plates, lenses and whole objectives; PA0 direct measuring of lengths and path length differences; PA0 measuring of optical inhomogeneities and streams. PA0 For measuring the spectral composition of light, they can usually be employed only for that light extending until the medium infrared range; for light in a more short-wave range there are considerable expenses for equipment; PA0 the planarity of the employed optical construction units must be excellent; and PA0 in a double-beam interferometer a precise guidance of the mirror, when moved, becomes indispensable. PA0 it broadens the spectral region of the polarization interferometer by a factor of one hundred as compared with the known Michelson arrangement, without increasing the expenses; and PA0 the single beam interferometer underlying the invention allows a robust design which is relatively insensitive to vibrations.
The known interferometers, however, provide the following disadvantages:
The invention alleviates the foregoing problem. The invention has the basic task to provide a polarization interferometer differing from the conventional apparatuses in so far as: